Engine Waste Heat Recovery: Latest MAN PTS-PTG System

Up to 5% of additional power can be extracted from the main engine exhaust gases by the first marine application of a new generation of Waste Heat Recovery (WHR) units from MAN Diesel & Turbo.

The order for the TCS-PTG 20 (Turbo Compound System with Power Turbine and Generator) units is for a pair of 4,700 TEU container ships being built for Germany’s Reederei Horst Zeppenfeld in the Samjin Shipbuilding in Weihai, China. These WHR units, which have recently passed their factory acceptance tests at MAN Diesel & Turbo’s Augsburg’s facility, will run alongside the MAN B&W 6S80ME-C9.2 low-speed main engines (rated at 27,060 kW) and the engine builders say they will also supply four TCA88 turbochargers, two for each ship.

Through using the TCS-PTG units, Zeppenfeld look not only towards saving fuel but for a reduction in the operating costs of their gensets as these can be run on part-load or switched off when the TCS-PTG units are in operation.

Briefly this is how the WHR system works: the power turbine is inserted into the exhaust gas system parallel to the turbochargers where it drives an electrical generator via a reduction gearbox and receives up to 13% of the exhaust gas flow, diverted from the main engine exhaust gas receiver, as shown in the diagram below.

Depending on the size of the MAN Diesel & Turbo engine involved, a maximum of 4,700 kW can be produced. The additional power output from the TCS-PTG system is in the form of 50 or 60 Hz electrical energy for the onboard power grid.

With this TCS-PTG 20 waste heat recovery ‘stand alone’ unit in operation, auxiliary engine fuel, emissions and maintenance costs can be saved and generator set maintenance more flexibly planned, since it can be carried out while while the ship is at sea.